Recently, portable terminals such as mobile phones have a wider range of uses and more abundant functions. Thus, performance requirements for portable terminals are increasing. Disclosed as a technology capable of providing a highly functional portable terminal is a technology in which a portable terminal can be separated unit by unit, e.g., into an image I/O unit and a voice receiving unit (see, e.g., Japanese Laid-Open Patent Publication Nos. 2005-176371 and 10-228458). This enables the user to enjoy highly functional services such as viewing images while speaking by phone.
A technique is disclosed in which for a portable terminal having dockable units, the units are connectable via a bus to devices (see, e.g., Japanese Examined Patent Publication No. H6-66057). Disclosed is a technique having a self-diagnostic circuit that diagnoses an abnormality or a failure in each of the units of the portable terminal (see, e.g., Japanese Laid-Open Patent Publication No. H3-217137).
In the above technologies, however, requirements for high performance lead to the necessity of high-performance processors being provided in the units, incurring increased cost. For example, the portable terminal separable into plural units requires a backup process as a result of separation into plural units and the arrangement of plural high-performance processors when performing function mirroring, which increases the cost.